1. Field of the Invention
The present invention relates to a separation method and apparatus/system for removing ions, contaminants and impurities from fluids such as water and other aqueous process streams, and more particularly, the present invention relates to a separation method and apparatus/system for desalinating water that uses engineered charged surfaces to sorb ions from salt solutions.
2. Description of Related Art
Conventionally, the separation of ions and impurities from electrolytes has been achieved using a variety of processes including: ion exchange, reverse osmosis, electro dialysis, electrodeposition, and filtering. In conventional reverse osmosis systems, for example, water is forced through a membrane, which acts as a filter for separating the ions and impurities from water. Reverse osmosis systems require significant energy to move the water through the membrane. The flux of water through the membrane results in a considerable pressure drop across the membrane. This pressure drop is responsible for most of the energy consumption by the process. The membrane also degrades with time, requiring the system to be shut down for costly and troublesome maintenance.
Other methods have been proposed and address the problems associated with conventional separation processes. However, these proposed methods have not been completely satisfactory and have not met with universal commercial success or complete acceptance. One such proposed ion separation method is a process for desalting water based on periodic sorption and desorption of ions on the extensive surface of porous carbon electrodes.
Other exemplary processes which further illustrate the problems associated with ion exchange include residential water softening and the treatment of boiler water for nuclear and fossil-fueled power plants. Such water softeners result in a relatively highly concentrated solution of sodium chloride in the drinking water produced by the system. Therefore, additional desalination devices, such as reverse osmosis filters are needed to remove the excess sodium chloride introduced during regeneration.
Based on still unsolved problems associated with conventional systems and because of a growing global shortage, there is still a significant and growing need for a new method and apparatus/system that lower all costs associated with water treatment, especially desalination. Energy use is of great importance because the cost of energy is approximately half the total cost of desalination of seawater using reverse osmosis, currently the most energy efficient sea water desalination technology.
Accordingly, a need exists for new desalination methods and apparatus that are more robust, that can lower capital and operating costs, that are more immune from scaling and fouling, and that are easier to clean than existing technologies while being continuous in operation, operator friendly, amenable to remote operation, and modular in design. The present invention is directed to such a need.